Abstract
Objectives of this study were to investigate the effects of milk replacer (MR) acidification for free- access feeding on pre- and post-weaning performance, morbidity and mortality of calves. Calves were randomly assigned to free-access feeding of acidified (ACID, n = 31) or non-acidified (NON, n = 31) MR, and weaned at 42 days. ACIDMR was prepared to pH 4.0 - 4.5 using formic acid. Intakes were measured daily and weights weekly. Samples of ACID and NON MR were analyzed for coliform and aerobic bacterial growth. After weaning, calves transitioned to a grain-fed veal diet, weighed every 2 weeks. At slaughter (approximately 6 months of age), lungs were evaluated for gross pathological changes and dressed carcass weights were obtained. Generalized linear mixed models were constructed to examine the effects of MR acidification. Differences by treatment group for pre- and post-weaning morbidity and mortality were tested using Pearson’s χ2 and Fisher’s exact tests. ACID calves consumed less MR than NON (10.6 vs. 11.7 L/d, P = 0.02). Acidification tended to promote earlier onset of starter ration consumption (32.0 vs. 39.5 d, hazard ratio = 1.5, P = 0.07), but did not affect average daily starter ration or water intakes across the pre-weaning period. ACID and NON calves did not differ for BW at weaning, pre- or post-weaning ADG or dressed carcass weight. ACID MR had less coliform (P < 0.001) and aerobic bacterial growth (P < 0.001) than NON MR, but odds of disease treatment and mortality did not differ. ACID calves tended to have lower odds of pulmonary lesions during post-mortem inspection than NON calves (OR = 0.3, P = 0.07). These results indicate that under free-access feeding conditions, acidification limited bacterial growth and MR intake, but there were no long-term impacts of acidification on calf performance or health. In conclusion, acidification to pH 4.0 - 4.5 will significantly reduce bacterial growth in milk fed to calves.
Highlights
Free-access milk feeding systems are increasingly adopted on dairy and veal farms [1] [2]
There is a need for research to validate whether this pH range is effective at limiting microbial growth under free-access feeding conditions in a commercial environment, and if this practice is associated with performance and health
Calves reared on the ACID and NON feeding treatments did not differ for birth body weight (BW) or serum total protein (TP) concentration
Summary
Free-access milk feeding systems are increasingly adopted on dairy and veal farms [1] [2]. With these feeding systems, milk is available continuously allowing calves to feed ad libitum and to have greater control over their feeding behavior [3] [4]. A practical challenge with free-access feeding is microbial growth when milk is kept at ambient temperatures [8]. Some dairy and veal producers add acid to milk to inhibit microbial growth under free-access feeding conditions [13] [14]. There is a need for research to validate whether this pH range is effective at limiting microbial growth under free-access feeding conditions in a commercial environment, and if this practice is associated with performance and health
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